The invention relates generally to a fuel injection system and method and, more specifically, to a system and method for operating a fuel injection system to reduce specific fuel consumption, engine exhaust emission, and fuel injector wear in an engine, e.g. turbocharged diesel engine.
In a compression-ignition engine, such as a diesel engine, a fuel injection system injects fuel (e.g., diesel fuel) into compressed air within each of the engine cylinders to create an air-fuel mixture that ignites due to the heat and pressure of compression. Engine efficiency, power output, fuel consumption, exhaust emissions, and other operational characteristics are trade-offs. Conventional techniques to improve one operational characteristic often worsen one or more other operational characteristics. For example, attempts to decrease specific fuel consumption often cause increases in various exhaust emissions characteristics. Vehicle exhaust emissions include pollutants such as carbon monoxide, nitrogen oxides (NOx), particulate matter (PM), and smoke generated due to incomplete combustion of fuel within the combustion chamber. The amount of these pollutants varies depending on the fuel-air mixture, compression ratio, injection timing, ambient conditions, and so forth.
Fuel injection systems generally employ fuel injectors, which open and fully close a valve for each commanded injection of fuel. Each injection of fuel causes wear on the valve due to the physical contact made between parts of the valve. Eventually, this wear can reduce performance and require servicing and/or replacement of the fuel injector. For example, significant wear can cause fuel leakage, undesirable changes in the fuel injection profile and so forth. In turn, this can result in a poor fuel-air mixture, which causes increased exhaust emissions.